The present invention relates generally to a method and a system for the management of availability and reliability of flash memory media.
For flash memory media, examples of metrics for life time include MTBF (Mean Time Between Failures), MTTF (Mean Time To Failure), and LDE (Long-term Data Endurance). MTBF is a general metric for HDD availability/reliability, and represents a statistic HDD life time. MTTF is a general metric for RAID group availability, and it represents a statistic RAID group life time. LDE is a metric that represents how much capacity the media can be written. An example of storage control for high availability/reliability is RAID (Redundant Array of Independent Disks). RAID 10 has 4 or more disks and stores double data. RAID 5 has 3 or more disks and stores data and parity data. The parity data is generated from the data. This optimized control method is described in U.S. Pat. No. 5,682,396. RAID 6 has 4 or more disks and stores data and double-parity data. The double-parity data are generated from the data.
Generally, the life of an HDD (Hard Disk Drive) is dominated by its running time, because an HDD medium has mechanical units (heads, platters and motors). However, the life of a flash memory medium is dominated by the number of times it is written (erase operation) since, when the erase operation occurs, the flash memory medium applies a high voltage to reset the data. This erase operation can cause damage. Meanwhile especially in the enterprise environment, the use of flash memory media for storage systems is required for its high transaction and throughput performance. It is important for these environments that the use of flash memory media not to be stopped due to failure.